In a press conference at 3pm BST today, Lazaridis said that all services are now back in operation around the world, and apologised again for the problems. He said that the company would begin a full investigation into what happened.

"We know we've let many of you down. You expect more from us. I expect more from us," he said.

In a statement, RIM added: "BlackBerry services are operating well globally. BlackBerry Support teams continue to monitor the situation around the clock to ensure ongoing service stability.

"Some customers in Canada and Latin America who are sending messages to other regions may see intermittent message delays. Support teams are actively addressing this."

RIM was keen to sort out the problems swiftly after it was criticised earlier in the week for claiming that services were operating normally, only to be contradicted by frustrated users.

Robin Bienfait, the chief information officer of RIM, also today apologised to customers for the issues.

"You've depended on us for reliable, real-time communications, and right now we're letting you down. We are taking this very seriously and have people around the world working around the clock to address this situation," he said.

"We believe we understand why this happened and we are working to restore normal service levels in all markets as quickly as we can."

RIM blamed the ongoing service problems on a massive backlog of emails in Europe, Asia and the Americas, following a "core switch failure" in one of its data centres.

The company admitted that this was the largest crash it had ever experienced, eclipsing the last major outage in 2009.